P3D Re: Stereo Window Demonstration

[donaldparks@xxxxxxxxxx]

George Themelis Wrote:

> you don't need to visualize the image in 3d in
> order to place the window in the right place.  Of course, the
> impact this adjustment means is understood only under
> stereoscopic examination.  That's why it is difficult to explain
> this concept to beginners with words and without the benefit of
> a real stereo picture.
>
> For our next club meeting I am scheduled for a demonstration of
> the stereo window.  I plan to cut open the top of an RBT mount
> and shift the rails while the slide is sitting inside my
> Brackett Dissolver stereo projector.  This will be a live
> demonstration of the stereo window.  The advantage of using the
> Brackett Dissolver over the TDC is that you can access the mount
> from the top while it is being projected with the BD, while you
> cannot do it with the TDC.

     Years ago I did a similar thing with an old Compco Projector.  I adapted a slide
carrier from a TDC 716 to fit in the Compco with a crude mechanism that allowed me to
grip one of the film chips and move it either horizontally or vertically while the
slide was being projected and viewed on the screen in 3D.  This was before Brackett
Dissolvers and RBT Mounts.  In those days I precision mounted my slides in folded
aluminum Realist masks and glass.  These masks permit you to move either film chip as
much as you want horizontally and a limited amount vertically.  I used the projection
mechanism to quickly and precisely align all my slides.  It was very helpful to be able
to view the enlarged images while horizontal and vertical adjustments to the film chip
were being made.

     The alignment method involved sliding the mask mounted slide into the viewing
position.  Then lock the mask firmly in place by pressing against it with a rubber
pad.  Position the film gripping fingers to the center of the film chip and close the
fingers to grip the film.  Use the projector's horizontal and vertical adjustments to
superimpose the left and right window frames.  Then turn the knobs of the positioning
mechanism to move the film chip horizontally or vertically as required to achieve the
desired mounting alignment.  Actually the best way to set the stereo window was to use
the projector's horizontal adjustment to cause a desired horizontal displacement
between the clearly visible left and right window frames.  Then move the film chip to
superimpose the images of a particular object in the slide that you want to be the
desired distance behind the stereo window.  Bingo you've set the stereo window.  Ungrip
the film. Unclamp the mask. Slide it out of the projector.  Secure the film chip more
permanently in the mask.  Tape the mask between sheets of glass and you're done.

     It sounds complicated but it's really quite intuitive once you can see both images
enlarged on the screen without the polaroid glasses and the 3D depth with the glasses
on.  The fingers get in the way a bit and block a small part of one image.  I may be
using the system again as I am becoming interested in taking stereo slides again.  I
still have this hardware and it still works.

    Don Parks

Dr. Donald J. Parks
Mechanical Engineering Dept.
Boise State University